2000 Outback 130k new to me.
It didn't have vibration when I boguht it 500 miles ago, now it does.
It feels like judder from 25-35, but there's also vibration at highway speeds.Also, it lightly 'clunks' (that I can feel more than hear) when the gas pedal is let off of then put back on.
The highway vibration is getting worse.

I added the magic goo (Lubegard 19610 Instant Shudder Fix) to the tranny 100 miles ago - no improvement in the vibration from 25-35 mph.

I'm thinking it may be the driveshaft carrier bearing or its rubber mount (but 130k is kinda low for that I'd think).
My question is: how to diagnose that without pulling the driveshaft. I had the car up and crawled under and pushed up and down on the driveshaft and it moved rather easily - I don't know if the rubber mount should alllow easy movement or if it should be stiffer, it just seemed rather soft to me.

The tranny mount just got replaced by a competent mcechanic. 

Any see-through-brick-walls folk out ther who can diagnose from a distance?
: -)

Thanks!

Put the FWD fuse in and see if it makes a difference.

Check your tyres for a bubble or something odd. 

I went through a process of eliminating parts from the back of my L series including removing the rear diff and driveshafts! Turned out one rear wheel developed a small bubble/egg on one side of the tread. 

Swapped the wheel and happy days! 

Do you feel it under the seat when the vibration occurs. Something similar in mine turned out to be drive shaft. Got an aftermarket since the u-joint was not replaceable and all was good.

 

Forgot to mention checking your wheel nuts are done up tight. This is a quick and easy check that could save a lot of headache!

I think that you are right to suspect the drive-shaft. The drive-shaft shouldn't be able to be moved by hand. It should be rigid, not soft - especially in the radial direction.

A passenger in the back seat might be able to tell where the vibration originates.